Seasonal Circulation in the Yellow and the East China Seas driven by the monsoon winds

Transcription

1 Seasonal Circulation in the Yellow and the East China Seas driven by the monsoon winds Ig-Chan Pang 1 and Jae-Hong Moon 2 1 : Cheju National University 2 : Department of Earth System Science and Technology, Kyushu University1

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3 Northward Expansion of Yellow Sea Warm Current Water in winter Southward Expansion of Yellow Sea Bottom Cold Water in summer from Kondo (1985)

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6 from Takikawa (2005 JGR)

7 Yellow Sea???

8 Water Mass Distributions Horizontal distributions of mean temperature and salinity at the depth of 0m and 50m in (A) February and (B) August data from GDEM Feb. Aug. The TWCW distribution expands northwestward in winter retreats southeastward in summer

9 The TWCW distribution expands northwestward in winter retreats southeastward in summer

10 Thermal Front in winter from the Kuroshio toward the YS in summer from the TS to the KTS Then, what current system makes these seasonal variations?

11 General description of Model (ROMS) Horizontal resolution : 1/8 degree Vertical resolution : 30-vertical levels Temperature and Salinity : WOA2001 (World Ocean Atlas, 2001) COADS (Comprehensive Ocean and Atmosphere Data Set ) - wind stress - heat flux and freshwater flux - heat flux sensitivity River source : Changjiang River discharge (Shen et al., 1994) Model domain and bottom topography (m)

12 In the adjacent seas of Taiwan Northerly wind Southerly wind current tracers winter summer Seasonal variation of transport in the TS No significant seasonal variation in the east of Taiwan related with the ECS

13 Without the monsoon winds Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec. Wind No wind in winter in summer The transport in the TS : not vary significantly in season without monsoon wind. critically influenced by monsoon wind.

14 In the central region of the ECS Northerly wind Southerly wind southward drift of China coastal water out of the YS northward drift of China coastal water into the YS pull water into the YS along the YS trough push water out of the YS along the YS trough winter summer in winter : northwestward current to the YS (* mostly flow out through the JS) in summer : northward current to the KTS (good agreement with the seasonal variations of the thermal front)

15 Without wind forcing no seasonal variation of the TWC and no seasonal circulation in the YS The seasonal variation of the TWC is caused by monsoon wind.

16 Relation with the seasonal circulation in the YS and the TS in winter in summer KOREA KOREA CHINA CHINA Kyushu Kyushu East China Sea East China Sea TAIWAN TAIWAN Seasonal variation of the TWC in the ECS related with the seasonal circulation in the YS and the seasonal variation in the TS, which are driven by the monsoon winds The TWC is mostly supplied from the Kuroshio in winter flow from the TS to the KTS in summer.

17 Influence by the variation of the Kuroshio The Kuroshio could not be the cause of the seasonal variation of transport in the KTS The transport variations in the Kuroshio and the KTS have different phases. The model transport in the east of Taiwan and the KTS

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19 Relation with the seasonal variation of the TWC The seasonal variation of the transport in the KTS is influenced by the TWC, which is connected with the wind-driven circulation in the YS

20 Relation with the monsoon winds If the transport in the KTS is influenced by monsoon wind, why does it have its maximum in October when the northerly winter monsoon wind start to blow instead of July or August when the southerly summer wind has its maximum? Monthly mean temperature distributions at the depth of 50m in (A) August and (B) October data from NFRDI (National Fisheries Research and Development Institute) during 1970~2000 Winter monsoon wind drives the warmer TWCW northward and colder coastal water southward to make the thermal front stronger.

21 Relation with the monsoon wind with wind forcing without wind forcing

22 Conclusion Conclusion The seasonal variation in the YECS are connected to comprise a large-scale seasonal circulation in the YECS. The seasonal circulation is driven by the monsoon wind. The maximum transport in the KTS in October is caused by the monsoon wind.

23 Thanks!

24 Jan. Feb. Mar. Apr. May Jun. Jul. Aug. Sep. Oct. Nov. Dec. Kuroshio PN line Tokara St ASUKA TS KTS JS Tsugaru St